Hydrocarbon fluids such as oil and natural gas are obtained from subterranean geologic formations, referred to as reservoirs, by drilling one or more wells that penetrate the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well is completed to and hydrocarbons may be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids.
Hydrocarbon wells for the exploitation of oil and/or gas from a reservoir normally consist of an upper and outer conductor, which forms the base of the well, an upper casing arranged into and in extension of the conductor, and further down in the well more casings which are arranged into and overlaps the above casing. A production tubing string (often referred to a production liner) is normally the innermost tubing of the well for transporting petroleum from the bottom of the well to the earth s surface or to the sea floor. The part of the casing arrangement that is set across the production zone is normally referred to as a “lower completion string”, a string that does not run all the way to the surface. Rather, it is hung from some location above the production zone. It is designed according to the conditions of the productive zone (the reservoir). Lower completion strings may be referred as: horizontal open hole completion, open hole sand control, slotted liner, predrilled liner, etc, and comprise the above mentioned production tubing string or production liner, as well as wellbore casings.
During production, there is a need to monitor the production inflow profile along the production zone. Production inflow profile is defined as the distributed inflow contributions along the production zone, and several monitoring systems and methods are known in the art. One traditional monitoring technique for obtaining such information is the wireline based Production Logging Tool (PLT).
The prior art also includes US 2007/0234788 A1, which describes a method of tracking fluid displacement along a wellbore using real-time temperature measurements. An optical conductor is installed in a wellbore casing and is configured to produce a temperature profile of the fluid flowing along the wellbore. One or more heat sources produce a temperature gradient in at least one fluid composition, and this temperature gradient is monitored along the wellbore by the optical conductor, to track fluid displacement along the wellbore. Due to the substantially different physical properties and rates of heat transfer between the adjacent fluid compositions and the wellbore, a variation in temperature gradient occurs in the wellbore as the interface between the fluid compositions displaces through the wellbore. By observing, in real-time, the position and displacement of the temperature gradient change, the corresponding position, displacement and flow rate of the fluid and its fluid compositions may be determined.
The prior art also includes US 2003/0140711 A1, which describes an apparatus comprising a temperature sensor for measuring and providing indication of the temperature of the fluid at least first and second temperature measuring points spaced by a known distance along the conduit; a heat exchanger selectably operable to alter the temperature of the fluid upstream from said temperature measuring points; and a timer, responsive to said output of said temperature sensor to measure the time difference of arrival of the temperature altered fluid at said first and second temperature measuring points. The conduit has a plurality of flow sources, and the apparatus comprises: a plurality of heat exchangers, each heat exchanger being downstream from a respective flow source; the temperature sensor being operative to measure and indicate the temperature at respective first and second points downstream from each heat exchanger; and the timer being operative to measure the time difference of arrival of temperature altered fluid at each respective pair of the first and second temperature measuring points. Thus, this publication describes an apparatus and a method which utilizes “time-of-flight” measurements for determining inflow profiles.
The prior art also includes U.S. Pat. No. 5,226,333 A, US 2013/0000398 A1, and SU 804825 A1, which also describe devices and methods of time-of-flight measurements for determining inflow profiles. In general, time-of-flight systems utilize heat sources that may be located anywhere upstream, and corresponding downstream temperature sensors. Cables are run along completion to cover multiple sensor positions along the production zone.
The prior art also includes US 2014/0343908 A1, which describes a method of estimating influx volumes of fluids to a production flow in a well. Tracer sources with unique tracer materials are arranged in fluid communication with two or more of the influx zones, and each tracer material has a predefined short duration release dose. Samples of the production flow are collected at the topside, and the samples are analyzed for identifying types of tracer material and concentration of the identified to tracer materials. The calculated influx volumes are utilized as parameters for controlling the production flow or for characterizing the reservoir.
It is a need for an improved system and method for monitoring the inflow profile along a wellbore production zone.